A nonwoven fabric is a web or continuous sheet of fibers laid down mechanically. The fibers may be deposited in a random manner or oriented in one direction. Most widely used fibers include cellulosics and synthetics including polyamides, polyesters, polypropylene and polyethylene. The spun fibers, which may be drawn, are laid down directly onto a belt by carding, airlaying or wet-laying. The sheet is then bonded together with a latex binder and subsequently treated in an oven or a calendar to complete the bonding process.
Commonly used latices for nonwoven fabrics are those prepared from polymers of butadiene-styrene, butadiene-acrylonitrile, vinyl acetate, acrylic monomers such as methyl acrylate, ethyl acrylate, methyl methacrylate and the like. It will be appreciated that to be useful as a nonwoven fabric in many applications, such as a permeable sublayer of a personal hygiene article, the latex binder should possess several desired physical properties. The desired physical properties include adequate tensile strength, a high modulus or stiffness under certain conditions, and good textile qualities such as tenacity, handle and the like.
It is an object of the present invention to provide a nonwoven fabric having a high modulus. It is another object of the present invention to provide a nonwoven fabric having desired physical properties. Yet another object of the present invention is to provide a nonwoven fabric of chemically bonded fibers that is simple and economical to manufacture.